How to create a copy of a python function

It does “copy” functions and classes (shallow and deeply), by
returning the original object unchanged;

I need a real copy, because I might change some attributes of the function.

Update:

I'm aware of all the possibilities which are mentioned in the comments. My use case is based on meta programming where I construct classes out of some declarative specifications. Complete details would be too long for SO, but basically I have a function like

def do_something_usefull(self,arg):
self.do_work()

I will add this method to various classes. Thoses classes can be completly unrelated. Using mixin classes is not an option: I will have many such functions and would end up adding a base class for each function. My current "workaround" would be to wrap this function in a "factory" like this:

That way I always get a new do_something_useful function, but I have to wrap all my functions like this.

You can trust me, that I'm aware, that this is no "normal" OO programming. I know how to solve something like that "normally". But this is a dynamic code generator and I would like to keep everything as lightweight and simple as possible. And as python functions are quite normal objects, I don't think it's too strange to ask how to copy them!?